This project sets out to specify further: (1) the origins of internal cues which signal an animal to eat or refrain from eating; (2) the neural locus for detection of such signals; (3) the potential associative role of these cues in the control of feeding. Experiments are proposed which require rats to use internal signals arising from their degree of food deprivation as discriminative cues for shock. The basic design requires that one group of rats receive mild foot-shock under one level of food deprivation (e.g., following 23 hr without food) and not receive shock under another level (e.g., 1 hr without food). Another group will receive the opposite deprivation level-shock contingency. Discrimination learning will be demonstrated to the extent that (1) each group shows greater amounts of conditioned freezing (i.e., skeletal immobility) under its shocked than under its nonshocked deprivation level and (2) the effects of deprivation level on freezing differs between groups. After both groups solve the discrimination problem, they will be tested for generalization between the deprivation cues conditioned during training and internal stimuli produced by various manipulations known to influence feeding (e.g., administration of insulin, 2-DG, CCK). Amount of generalization will serve as an index of degree to which the rats evaluate the internal stimuli produced by the manipulation as the same as those produced by food deprivation. The unique feature of this design is that it avoids or reduces several potenconfounds associated with the use of feeding as the index of hunger or satiety. This research also investigates whether or not internal food deprivation-- produced cues can become conditioned modulators of feeding. These studies examine the degree to which food deprivation signals can become Pavlovian conditioned inhibitors or conditioned facilitators, and investigate whether or not manipulations known to affect the development of Pavlovian facilitation have parallel effects on the capacity of food deprivation to moderate feeding behavior. It is hoped that this research with animals will help improve our understanding of mechanisms controlling maladaptive feeding behavior in humans.